1. Field of the Invention
This invention relates to anastomosis devices and methods of anastomosis and more particularly, though not exclusively, relates to the anastomosis of small blood vessels in the human body.
2. Brief Description of the Prior Art
Accurate and complete anastomosis methods are necessary for successful microvascular surgery. It is often important that the anastomosis be performed in a minimal amount of time in order that tissue damage be avoided, that anaesthesia time is minimized and that the healing process be begun as soon as practicable. The anastomosis should provide a blood-tight seal, yet maintain good patency for blood flow. The presence of any material on the inside of the vessel should preferably be avoided as it can provide a nidus for clot formation. It is also desirable that the blood vessel have the ability to maintain a certain degree of its normal pulsatile action at the point of anastomosis. In addition, anastomosis must often be performed on blood vessels with diameters as small as one millimeter or less, therefore a successful anastomosis technique should be adaptable to such small dimensions.
The refinements of technique in microvascular surgery have developed in two directions. The first approach is the use of microsuture techniques. These surgical techniques have advanced with the aid of the development of operating microscopes, microsutures and microinstruments. They produce very accurate anastomosis and yield good patency. However, the techniques have not been widely used because they not only have the disadvantage of being time consuming, but they also have the disadvantage of requiring an extremely high degree of technical skill. The presence of suture material in the interior of a blood vessel can also present a nidus for clot formation.
The second approach has been in the direction of various mechanical devices or glues which attempt to circumvent the exacting skill and prolonged time required for the suturing techniques. The glues have generally been unsuccessful because of complications involving tissue toxicity and reaction. Stapling techniques have been cumbersome and have been difficult to use on vessels under 2 mm. in size. Other devices have included various tubes, flanges and rings. The rigidity of these devices has presented a problem of functional obstruction during pulsatile flow. The necessity for either everting one end of the vessel or stretching it over the rigid devices makes these anastomosis methods more difficult for smaller vessels.
Zack U.S. Pat. No. 2,453,056 is one such rigid anastomosis device. It is tubular in structure, has a longitudinal slot which permits partial compression and has ring-like clamps which slide over the structure to maintain the vessels in position. Upon compression, the longitudinal slot causes reduction in the surface of the cylindrically shaped device to occur only at the position of the slot and not uniformly about the cylinder. Moreover, the compression of the ring-like clamps may adversely affect the health of the compressed tissue. The Zack device does not have the capability of contraction and expansion during pulsatile flow. Lastly, the ring-like clamps can potentially slide off of the device and thus disrupt the anastomotic mend.
Brown U.S. Pat. No. 3,155,095 and Noble U.S. Pat. No. 3,221,746 are two more examples of rigid anastomosis devices. The Brown device is composed of absorbable material over which the ends of the vessels are stretched and has external clamps similar to the Zach patent. Noble uses hooks as a means for attachment. Both of these devices require the stretching of the ends of the blood vessels over the rigid devices and has considerable exposed surface area in the interior portion of the mended blood vessel. This exposure can provide a nidus for clot formation, can cause obstruction of normal blood flow and their rigidity prevents the vessel from pulsating normally.
Razgulov U.S. Pat. No. 3,908,662 is an eversion device and vascular stapling instrument. This device illustrates the state of the art in vascular stapling techniques for purposes of anastomosis. A portion of the instrument includes a rigid, slotted tubular structure (somewhat resembling the Zack device) that is used as a bushing about which the end of a vessel is everted.
Bucalo U.S. Pat. No. 3,938,528 is another rigid anastomosis device. It uses hooks as a means of attachment and, when in place, is entirely in the internal portion of the blood vessel. As with other rigid devices, this device has no ability to accomodate pulsatile expansion to any degree.
Some non-analogous prior art shows the existence of "s"-shaped metal wire, cylindrical tension devices (see, e.g., Wilkening U.S. Pat. No. 2,293,450). Such devices would not be suitable for use as anastomosis devices even if they had been considered for a number of reasons: (1) They generally are not made of a material which is suitable for implantation into the body. (2) They generally are much too large, not only in diameter, but also in some instances, in the number of "s"-shaped loops. (3) They generally have an undesirable height to diameter ratio. (4) They generally do not have associated barbs which could serve to retain either a snare loop or blood vessels.
Wells U.S. Pat. No. 1,672,591 is a nostril dilator that is essentially a lateral spring mechanism comprising a series of loops. Although it is a spring-like device, this patent is considerably different in structure from the preferred embodiment of the present invention in that it is not radially resilient and is comprised of loops instead of "s"-shaped elements. In use of the Wells device, the outward pressure supplied is only in two directions and the Wells device itself would be much too large to be used with a blood vessel. The Wells device also does not have associated barbs which could serve to retain either a snare loop or blood vessels.